NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
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RS-485 Auto Address Detection Operation Mode (AAD)
In RS-485 Auto Address Detection Operation Mode, the receiver will ignore any data until an address
byte is detected (bit9 =1) and the address byte data match the ADDR_MATCH(UA_ALT_CSR[31:24])
value. The address byte data will be stored in the RX-FIFO. The all received byte data will be
accepted and stored in the RX-FIFO until and address byte data not match the
ADDR_MATCH(UA_ALT_CSR[31:24]) value. In RS-
485 AAD mode, don’t fill any value to
RX_DIS(UA_CTL[2]) bit.
Program Sequence example:
1. Program FUN_SEL(UART_FUN_SEL[1:0]) to select RS-485 function.
2. Program the RS485_AAD(UA_ALT_CSR[9]).
3. When an address byte is detected (bit9 = “1”), hardware will compare the address byte and the
ADDR_MATCH (UA_ALT_CSR[31:24]) value.
4. If the address byte matches the ADDR_MATCH(UA_ALT_CSR[31:24]) value, hardware will set
RLS_IS(UART_ISR[2]) and RS485_ADD_DETF(UA_FSR[3]). And the receiver will sorted address
byte to FIFO and accept the following data transfer and stored data in FIFO until next address byte be
detected.
However if the address byte does not match the ADDR_MATCH(UA_ALT_CSR[31:24]) value,
hardware will ignored the address byte data and ignored the following data transfer.
5. Respect step 3 and step 4.